[Vxl-maintainers] to parse EXIF meta data in JPEG image files

Hi Folks,
Does anyone have experience with extracting EXIF meta data from JPEG
images? As far as I know, vil does not have this functionality (yet).
I am kind of probing around and see if anyone in VXL community has
this knowledge.
One way for me to accomplish this is to exploit a 3rd party library,
e.g., libexif or Exiv2, and place it in my own project. On the other
hand, before making the decision and getting down the path of
implementation, It will be good to know if anyone is also interested
in this functionality.
Thanks.
Gehua Yang

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Hi Folks,
Does anyone have experience with extracting EXIF meta data from JPEG
images? As far as I know, vil does not have this functionality (yet).
I am kind of probing around and see if anyone in VXL community has
this knowledge.
One way for me to accomplish this is to exploit a 3rd party library,
e.g., libexif or Exiv2, and place it in my own project. On the other
hand, before making the decision and getting down the path of
implementation, It will be good to know if anyone is also interested
in this functionality.
Thanks.
Gehua Yang

Gehua,
I have no experience with EXIF nor do I have an immediate use for
it, but I do think it would be a useful addition to vil. I'd be happy
to see you add this directly to vil if you are working on it anyway.
--Matt
On Tue, Jul 1, 2008 at 11:20 AM, Gehua Yang <yanggehua@...> wrote:
> Hi Folks,
>
> Does anyone have experience with extracting EXIF meta data from JPEG
> images? As far as I know, vil does not have this functionality (yet).
> I am kind of probing around and see if anyone in VXL community has
> this knowledge.
>
> One way for me to accomplish this is to exploit a 3rd party library,
> e.g., libexif or Exiv2, and place it in my own project. On the other
> hand, before making the decision and getting down the path of
> implementation, It will be good to know if anyone is also interested
> in this functionality.
>
> Thanks.
> Gehua Yang
>
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Hi
We have never used it, but getting more info out of JPEG files would
always be useful. I'd be particularly interested in getting the
resolution info out.
If you incorporate the EXIF reading into
core/vil/file_formats/vil_jpeg.* then you could either write your own
parser, or add libexif to v3p and use that. If you only have a few small
tags you are interested in then the former approach might be easier overall.
Regards,
Ian.
Gehua Yang wrote:
> Hi Folks,
>
> Does anyone have experience with extracting EXIF meta data from JPEG
> images? As far as I know, vil does not have this functionality (yet).
> I am kind of probing around and see if anyone in VXL community has
> this knowledge.
>
> One way for me to accomplish this is to exploit a 3rd party library,
> e.g., libexif or Exiv2, and place it in my own project. On the other
> hand, before making the decision and getting down the path of
> implementation, It will be good to know if anyone is also interested
> in this functionality.
>

Hi all,
It looks like a few people are interested in having this functionality in vil.
One obstacle is about how to *access* the meta data once it is loaded.
The best candidate solution I can come up with so far is to utilize
vil_property. The benefit is that we do not need to change much of the
existing functions or to add new ones. However, there are a few issues
that must be addressed before we can proceed with this approach:
1) Addition of tags: The number of standard tags defined in EXIF is
quite large (see the link below). Of course we can manually add only
those commonly-used ones into vil_property.h. Or we can use the tags
as it is, "Exif.Image.DateTime" for instance, without polluting the
vil_property.h header file.
http://www.exiv2.org/metadata.html
2) Potential security hazard: since the
vil_image_resource::get_property() function does not have any boundary
checks, it is possible for some bad guy to overflow a memory buffer
with a particularly long string embedded in a image. Are we going to
just let it be or somehow force a check?
3) Data types: The "Rational" data structure has to be introduced into
vil before tags such as "Exif.Photo.ExposureTime" can be assessed.
Though vnl has vnl_rational, because both are level 1 libaries, vil
cannot use vnl_rational.
I guess for now I will implement this functionality in my internal
project. Once I am confident enough about my implementation and also
these issues are cleared, I'll try to put it in vil. Comments and
suggestions are welcome!
Sincerely,
Gehua
On Tue, Jul 1, 2008 at 11:50 AM, Ian Scott
<ian.m.scott@...> wrote:
> Hi
>
> We have never used it, but getting more info out of JPEG files would always
> be useful. I'd be particularly interested in getting the resolution info
> out.
>
> If you incorporate the EXIF reading into core/vil/file_formats/vil_jpeg.*
> then you could either write your own parser, or add libexif to v3p and use
> that. If you only have a few small tags you are interested in then the
> former approach might be easier overall.
>
> Regards,
> Ian.
>
>
>
> Gehua Yang wrote:
>>
>> Hi Folks,
>>
>> Does anyone have experience with extracting EXIF meta data from JPEG
>> images? As far as I know, vil does not have this functionality (yet).
>> I am kind of probing around and see if anyone in VXL community has
>> this knowledge.
>>
>> One way for me to accomplish this is to exploit a 3rd party library,
>> e.g., libexif or Exiv2, and place it in my own project. On the other
>> hand, before making the decision and getting down the path of
>> implementation, It will be good to know if anyone is also interested
>> in this functionality.
>>
>
>